The present invention relates to magnetic tape drives, and in particular, to a mechanism of a magnetic tape drive for opening an access door of a tape cartridge such that the cartridge can be inserted into the drive in a direction parallel to the long dimension of the cartridge and drive, and such that the cartridge will be operatively positioned in the drive upon insertion therein. The present invention also relates to a mechanism for detecting full insertion of the tape cartridge.
One of the problems which has been encountered in the art is that of inserting a magnetic tape cartridge with its long dimension parallel to the insertion direction (hereinafter referred to as "longitudinal insertion") into a tape drive. This problem is particularly acute in the case of inserting a cartridge such as that manufactured by Minnesota Mining & Manufacturing Co. (hereinafter, a "3M-type cartridge") into a 5-1/4" form factor tape drive. The 3M-type cartridge has a length of 6", a width of 4" and a pivotably mounted access door along one of the 6" sides. When the axis door is opened, the total width of the cartridge is roughly 5-3/4". Such a cartridge 52 is shown in FIG. 11.
In most tape drives, the cartrige 52 is inserted in the direction of the arrow A, thus requiring an insertion slot width which is equal to the length 1.sub.1, of the cartridge. To make the drive smaller, it has been proposed to insert the cartridge 52 in the direction of the arrow B. It is further desireable to insert the cartridge into a 5-1/4" form factor tape drive, which is a rectangular prism of no larger than 3-1/4" by 5-3/4" by 8". Since the width of the 3M-type cartridge with the access door open is substantially the same as the maximum width of the 5-1/4" form factor tape drive, it is difficult to provide a simple, inexpensive mechanism for opening the access door of the cartridge and at the same time, achieving longitudinal insertion. Moreover, in a drive in which the cartridge is longitudinally inserted, the magnetic head is generally moved into engagement with the magnetic tape, which is exposed when the access door is opened, by a single-axis link, for example, after the cartridge has been inserted into the frame. Therefore, more than one operation is necessary to insert the cartridge and move the head into engagement with the tape.
One drive which achieves longitudinal insertion is disclosed in U.S. Pat. No. 4,573,091. The drive has an open front end through which a longitudinally extending tray moves. With the tray extended, a cartridge is placed thereon and the tray is retracted. The access door is opened by a spring-biased pin mounted on the tray and linked to a longitudinal side of the drive such that the pin opens the access door during retraction of the tray. Only after the tray and cartridge have been completely retracted into the drive can a load lever on the front of the drive be rotated to move a magnetic head into contact with the surface of the tape exposed by the access door. Moreover, the drive has an open front end which increases the chances that foreign objects will enter the drive and deposit on the head or tape. Further problems with drives of this type are that reliability of proper insertion is not as high as desirable, and that the design is complex requiring an increased number of parts. For example, in order to detect when the tray has been moved into the housing and when the cartridge is in the operative position in the housing, two microswitches are necessary to perform these respective operations. The number of required parts is increased. Moreover, even if the microswitches are intended to simultaneously detect proper positioning of the frame and cartridge, it is difficult to actually actuate the two switches at the same time due to limitations on the accuracy of the switches.
Another drive in which longitudinal insertion is achieved is disclosed in U.S. Pat. No. 4,622,606. A cassette is inserted longitudinally into a tunnel-like insertion channel in a housing. A channel cover is then rotated closed, and in response thereto, a complex link and swivel arm mechanism opens the access door of the cassette. A leaf spring provided at the rear of the housing to prevent full insertion of the cassette prior to opening of the access door. However, if too much force is used to insert the cassette, the leaf spring will yield. Thus, full insertion of the cassette can occur prior to opening of the access door and there is a chance that the magnetic head will collide with the access door. Moreover, as the channel cover is provided on the housing, the cartridge must be most of the way into the drive when the access door is opened. Therefore, the magnetic head must be provided relatively far from its operative position to avoid being struck by the access door during opening thereof.